The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Routers in packet data networks that use Internet Protocol (IP) and Border Gateway Protocol (BGP) perform a convergence process to resolve routing paths among nodes in the network. The convergence process often requires considerable time to perform in networks that have large numbers of nodes. Network administrators of large networks generally desire to reduce convergence time whenever possible.
Presently, in interior BGP (IBGP) network deployments, an IBGP software module in a router may have information about an alternate route that is feasible and desirable, but the IBGP module may under some circumstances conclude that there is no reachability in subsets of the IBGP domain. This may occur, for example, when IGP reachability to the BGP next hop has been lost. In the event that local but internal reachability changes occur, present operation of IBGP modules can lead to churn in the IBGP networks, which also affects EBGP peers. Such behavior is severely detrimental to networks of Internet Service Providers (ISPs). For example, when ISPs have deployed network-monitoring tools such as Cisco Optimized Edge Routing (OER), ISPs can begin to lose traffic and business revenue because traffic is re-routed incorrectly due to such transient changes. This transient behavior also affects the basic convergence properties of the BGP protocol. Therefore, network administrators desire a solution to address such transients and be able to rapidly arrive at correct reachability information within IBGP domains, and assist in IBGP domains quickly converging to a common understanding of reachability.
Further, administrators of service provider networks would like to constrain all updates that are sent out of their domain of administrative control, which may comprise multiple autonomous systems, to only those updates that represent the final state of connectivity through their network. In present approaches, BGP modules may send update messages that do not reflect the final connectivity state, as a result of limitations in path vector protocols when deployed for intra-domain routing table management.
While solutions to the foregoing issues are needed, any solution must also consider existing network constraints. For example, the amount of available data storage space in provider edge (PE) routers is finite, and any solution that uses an unreasonable amount of storage will be untenable.